Amino Vinylsilane Precursors for Stressed SiN Films

ABSTRACT

The present invention is a method to increase the intrinsic compressive stress in plasma enhanced chemical vapor deposition (PECVD) silicon nitride (SiN) and silicon carbonitride (SiCN) thin films, comprising depositing the film from an amino vinylsilane-based precursor. More specifically the present invention uses the amino vinylsilane-based precursor selected from the formula: [RR 1 N] x SiR 3   y (R 2 ) z , where x+y+z=4, x=1-3, y=0-2, and z=1-3; R, R 1  and R 3  can be hydrogen, C 1  to C 10  alkane, alkene, or C 4  to C 12  aromatic; each R 2  is a vinyl, allyl or vinyl-containing functional group.

CROSS REFERENCE TO RELATED APPLICATIONS

The Present application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/113,624 filed Nov. 12, 2008.

BACKGROUND OF THE INVENTION

The Present Invention is in the field of integrated circuit fabricationand particularly materials of construction in the films that areadjacent to or are a part of electronic devices in the integratedcircuit, such as transistors, capacitors, vias, electrically conductivelines and buss bars. As the dimensions of such electronic devicescontinue to shrink and the density of such devices in a given areaincreases, the films adjacent to or a part of such electronic devicesmust exhibit higher electrical properties. Designing stress into suchfilms can alter their electrical properties. Stress engineering of PECVDsilicon nitride films is currently being used to enhance the performanceof cutting edge metal oxide semiconductor field effect transistor(MOSFET) technology. Device speed has been significantly increasedthrough the application of highly stressed SiN films deposited on top ofMOSFET gate structures. Compressive stress enhances “P” type fieldeffect transistors (pFET) devices through increases of hole mobility,while tensile stress is beneficial for “N” type field effect transistors(nFET) devices through enhancing electron mobility. Stress is generatedfrom differences in the thermal expansion between two materials incontact. Plasma enhanced chemical vapor deposition (PECVD) siliconnitride films generally generate compressive stress.

Presently, compressively stressed films are deposited using silane andammonia with reported compressive stresses up to ˜−3.5 giga pascales(GPa). Increasing compressive stress further is becoming particularlychallenging. The industry is currently aiming for compressively stressedfilms of −4 GPa or higher.

Patents related to this technology include: US 2006/0045986; EP 1 630249; US 2006/0258173; EP 1 724 373; U.S. Pat. No. 7,288,145; U.S. Pat.No. 7,122,222; US20060269692; WO2006/127462; and US2008/0146007, as wellas the literature reference; “Methods of producing plasma enhancedchemical vapor deposition silicon nitride thin films with highcompressive and tensile stress.”; M. Belyansky et al. J. Vac. Sci.Technol. A 26(3),517 (2008).

BRIEF SUMMARY OF THE INVENTION

The present invention is a method to increase the intrinsic compressivestress in plasma enhanced chemical vapor deposition (PECVD) siliconnitride (SiN) and silicon carbonitride (SiCN) thin films, comprisingdepositing the film from an amino vinylsilane-based precursor.

More specifically the present invention uses the amino vinylsilane-basedprecursor selected from the formula: [RR¹N]_(x)SiR³ _(y)(R²)_(z)

where x+y+z=4, x=1-3, y=0-2, and z=1-3; R, R¹ and R³ can be hydrogen, C₁to C₁₀ alkane, alkene, or C₄ to C₁₂ aromatic; each R² is a vinyl, allylor vinyl-containing functional group.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIGS. 1 A and B are depictions of structural formulae of species ofchemical precursors for the present invention.

FIG. 2 is a graph of stress values for films formed by PECVD depositionsof BIPAVMS and ammonia under various process conditions.

FIG. 3 is a FTIR spectra of silicon nitride films deposited with PECVDusing BIPAVMS and ammonia.

FIG. 4 is a graph plotting the ratio of nitrogen bonded hydrogen(NH_(x)) to silicon bonded hydrogen (SiH) content versus film stress.

FIG. 5 is a graph plotting NH_(x) and SiH content versus film stress.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides amino vinylsilane-based precursors as away to increase the intrinsic compressive stress in plasma enhancedchemical vapor deposition (PECVD) silicon nitride (SiN) and siliconcarbonitride (SiCN) thin films. The main feature of these aminovinylsilane precursors is one or two vinyl functional groups bonded tothe central silicon atom. The precursors have the general formula:

[RR¹N]_(x)SiR³ _(y)(R²)_(z)

where x+y+z=4, x=1-3, y=0-2, and z=1-3. R, R¹ and R³ can be hydrogen, C₁to C₁₀ alkane, alkene, or C₄ to C₁₂ aromatic; each R² is a vinyl, allylor other vinyl-containing functional group. The addition of a vinylgroup to the aminosilane is found to increase the intrinsic compressivestress of SiN and SiCN films deposited using these precursors.

The amino vinylsilane precursors include, but not limited to,Bis(isopropylamino)vinylmethylsilane (BIPAVNS),Bis(isopropylamino)divinylsilane (BIPADVS),Bis(isopropylamino)vinylsilane, Bis(isopropylamino)allylmethylsilane,Bis(isopropylamino)diallylsilane, Bis(isopropylamino)allylsilane,Bis(t-butylamino)vinylmethylsilane, Bis(t-butylaminoamino)divinylsilane,Bis(t-butylaminoamino)vinylsilane,Bis(t-butylaminoamino)allylmethylsilane,Bis(t-butylaminoamino)diallylsilane, Bis(t-butylaminoamino)allylsilane,Bis(diethylamino)vinylmethylsilane, Bis(diethylamino)divinylsilane,Bis(diethylamino)vinylsilane, Bis(diethylamino)allylmethylsilane,Bis(diethylamino)diallylsilane, Bis(diethylamino)allylsilane,Bis(dimethylamino)vinylmethylsilane, Bis(dimethylamino)divinylsilane,Bis(dimethylamino)vinylsilane, Bis(dimethylamino)allylmethylsilane,Bis(dimethylamino)diallylsilane, Bis(dimethylamino)allylsilane,Bis(methylethylamino)vinylmethylsilane,Bis(methyethylamino)divinylsilane, Bis(methyethylamino)vinylsilane,Bis(methyethylamino)allylmethylsilane,Bis(methyethylamino)diallylsilane, Bis(methyethylamino)allylsilane,Dipiperidinovinylmethylsilane, Dipiperidinodivinylsilane,Dipiperidinovinylsilane, Dipiperidinoallylmethylsilane,Dipiperidinodiallylsilane, Dipiperidinoallylsilane,Dipyrrolidinovinylmethylsilane, Dipyrrolidinodivinylsilane,Dipyrrolidinovinylsilane, Dipyrrolidinoallylmethylsilane,Dipyrrolidinodiallylsilane, Dipyrrolidinoallylsilane.

The particular precursor used in tests isBis(iso-propylamino)vinylmethylsilane (BIPAVMS). Another similarprecursor is Bis(iso-propylamino)divinylsilane (BIPADVS).

Stress engineering of PECVD silicon nitride films is currently beingused to enhance the performance of cutting edge MOSFET technology.Device speed has been significantly increased through the application ofhighly stressed SiN films deposited on top of MOSFET gate structures.Compressive stress enhances pFET devices through increases of holemobility, while tensile stress is beneficial for nFET devices throughenhancing electron mobility. Stress is generated from differences in thethermal expansion between two materials in contact. PECVD siliconnitride films generally generate compressive stress. Presently,compressively stressed films are deposited using silane and ammonia withreported compressive stresses up to ˜−3.5 GPa. Increasing compressivestress further is becoming particularly challenging. The industry iscurrently aiming for compressively stressed films of −4 GPa or higher.

The goal of −4 GPa compressively stressed films may be realized throughthe use of the above described amino vinylsilane precursors. In thepresent invention, compressive stress of −0.7 to −4.5 GPa (−700 to −4500MPa) can be obtained. Up to now, most of the increases in stressgeneration have been through processing techniques, such as plasmasurface treatment, multilayer deposition, dual frequency plasma andother similar methods. This invention is the first to specifically use aunique type of silicon-containing precursor to increase film stress.

Standard deposition methods have a limit to the amount of stress theycan generate. Current targets for stress are 1.5 GPa for tensile stressand −4 GPa for compressive stress.

It has been observed that higher hydrogen incorporation into SiN filmsleads to higher compressive stress. We propose that PECVD SiN filmsdeposited using amino vinylsilanes such as BIPADVS and BIPAVMS cangenerate highly compressive stress due to overall hydrogen incorporationand, moreover, through the type of hydrogen incorporation, i.e. nitrogenbonded hydrogen vs silicon bonded hydrogen. We have shown for bothbis(tertiary-butylamino)silane (BTBAS) and BIPAVMS a strong correlationbetween N—H to Si—H ratio and compressive stress, with high N—H to Si—Hratio leading to higher compressive stress. Films deposited using amixture of an aminosilane and ammonia naturally lead to films containinghigh N—H to Si—H content through transamination reactions

Furthermore, aminosilanes containing vinyl functional groups, such asBIPADVS and BIPAVMS, have been found to increase compressive stressfurther. Vinyl groups play important roles in creating film stress.Under plasma conditions, carbon-carbon double bonds may formcross-linking points, which increase the density of film by holdingatoms closer. Si—H bonds of the precursor react with carbon-carbondouble bonds with hydrosilylation reaction, forming ethylene bridgesbetween silicon atoms. Ethylene bridges hold the silicon atoms close,and are consequently replaced by ammonia, and that process helps theformation of Si—N—Si structure.

The present invention is directed to overcome limits of intrinsic stressgeneration through the use of this special class of aminosilaneprecursors, namely amino vinylsilanes, to deposit highly stressedsilicon nitride (SiN) films or silicon carbonitride (SiCN) films usingPEVCD. The addition of a vinyl group to the aminosilane is found toincrease the intrinsic compressive stress of SiN and SiCN filmsdeposited using these precursors.

To deposit compressively stressed silicon nitride or siliconcarbonitride films, the amino vinylsilane is reacted with anitrogen-containing gas in a PECVD chamber at wafer temperatures of 500°C. or less. The nitrogen containing gas can be ammonia, nitrogen, or acombination thereof. Additionally, a diluent gas such as, but notlimited to, He, Ar, Ne, Xe, or hydrogen can be introduced to modify thefilm properties. For example, Bis(iso-propylamino)vinylmethylsilane(BIPAVMS) (FIG. 1 A) or Bis(iso-propylamino)divinylsilane (BIPADVS)(FIG. 1 B) and ammonia are introduced into a PECVD chamber and allowedto react, resulting in the deposition of a compressively stressed SiNthin film. A suitable BIPAVMS flow rate may range from 50 to about 1000mg/min. A suitable ammonia and/or nitrogen flow rate may range from 500to 10,000 sccm, and the diluent gases can range from 50 to 50,000 sccm.

Example

Depositions conditions for Runs A-F and the corresponding film stressobtained in Table 1, below, are as follows. Deposition temperature was400 C. In these examples, properties were obtained from sample filmsthat were deposited onto medium resistivity (8-12 Ωcm) single crystalsilicon wafer substrates. All depositions were performed on an AppliedMaterials Precision 5000 system in a 200 mm DXZ chamber fitted with anAdvanced Energy 2000 RF generator. The plasma is single frequency of13.56 MHz.

In the Table 1 examples, thickness and optical properties, such asrefractive index of the dielectric films, were measured on an SCIFilmtek Reflectometer. The refractive index is measured using 632 nmwavelength light. Fourier Infrared Spectroscopy (FTIR) data wascollected on the wafers using a Thermo Nicolet 750 system in a nitrogenpurged cell. Background spectra were collected on similar mediumresistivity wafers to eliminate CO₂ and water from the spectra. Data wasobtained in the range of from 4000 to 400 cm⁻¹ by collecting 32 scanswith a resolution of 4 cm⁻¹. The OMNIC software package was used toprocess the data. Film stress measurements were made using a laser beamscattering tool (Toho Technology Corp., Model: FLX2320S).

TABLE 1 BIPAVMS flow NH3 P Power Stress Film (mg/min) (sccm) (Torr) (W)(MPa) A 250 2500 2.5 400 −1849 B 250 1250 2.5 400 −934 C 250 2500 4 400−757 D 250 2500 2.5 600 −2249 E 125 2500 2.5 400 −2357 F 125 2500 2.5600 −2260

Film stress data of silicon nitride films deposited at 400° C. usingBis(iso-propylamino)vinylmethylsilane and ammonia is shown in FIG. 2.The films were deposited under various process conditions, such asprecursor and gas flow rate, pressure, and RF power. The films weresingle layer, with thicknesses ranging from 100 to 350 nm. The plasmawas generated using a single frequency of 13.56 MHz. The compressivestress of these films ranged from −700 to −2400 mega pascales (MPa).These films produced ˜1.5 to 1.8× higher compressive stress, than BTBASunder comparable process conditions.

FIG. 3 shows the FTIR spectra of films from FIG. 2 with the lowest (FilmC) and highest (Film E) compressive stress. Both films exhibit NH_(x)stretching and bending modes of similar intensity. However, there is adistinct difference in the SiH peak at ˜2190 cm⁻¹, thus suggesting themain difference is in whether hydrogen is bonded to nitrogen or silicon.

FIG. 4 depicts the correlation between the ratio of NH_(x) to SiH withstress. As can be seen from this figure, stress increases with higherNH_(x) to SiH ratio. Preferably, the deposited thin film has a N—H toSi—H ratio of 25 to 85, most preferably 70.

FIG. 5 depicts the correlation of nitrogen bonded hydrogen (NH_(x)) tostress and silicon bonded hydrogen to stress. This data indicates thatreduction of SiH groups in addition to high levels of NH_(x) moiety isimportant in generating high levels of compressive stress. Hydrogencontents derived from NH_(x) moieties increase compressive stress in therange of 2.9 to 3.5 H content/cm³×10²², preferably 3.3 to 3.6 Hcontent/cm³×10²²

Experimental data indicate that films possessing higher stress valueswere found not to contain carbon. It is inferred that the carbon isetched away by the ammonia, which is in high excess compared to theprecursor. In higher stress SiN films, more Si—H bonds are removed bythe hydrosilylation of vinyl group, and replaced with N—H by the removalof ethylene bridge by ammonia.

Example 2

Under process condition A listed in Table 1, the stress of films usingnon-vinyl precursor (such as BTBAS) is lower than that for (BIPAVMS)

TABLE 2 Thickness Dep. Rate Stress Precursor (nm) (nm/min) RI (MPa)BIPAVMS 208 13.9 1.97 −1849 BTBAS 136 13.6 1.97 −1034

Example 3

Under process condition A listed in Table 1, but an alternative tool andshowerhead configuration, the stress of films deposited increases as thenumber of vinyl groups increases in precursor.

TABLE 3 Precursor Vinyl groups Stress (MPa) BIPAVMS 1 −1200 BIPADVS 2−1705

1. A method to increase the intrinsic compressive stress in plasmaenhanced chemical vapor deposition (PECVD) of silicon nitride (SiN) andsilicon carbonitride (SiCN) thin films, comprising depositing the filmfrom an amino vinylsilane-based precursor.
 2. The method of claim 1wherein the amino vinylsilane-based precursor is selected from theformula: [RR¹N]_(x)SiR³ _(y)(R²)_(z) where x+y+z=4, x=1-3, y=0-2, andz=1-3; R, R¹ and R³ can be hydrogen, C₁ to C₁₀ alkane, alkene, or C₄ toC₁₂ aromatic; each R² is a vinyl, allyl or vinyl-containing functionalgroup.
 3. The method of claim 2 wherein the amino vinylsilane basedprecursor is selected from the group consisting ofBis(iso-propylamino)vinylmethylsilane (BIPAVMS),Bis(iso-propylamino)divinylsilane (BIPADVS) and mixtures thereof.
 4. Themethod of claim 1 wherein the compressively stressed films have acompressive stress of −4 GPa or higher.
 5. The method of claim 1 whereina nitrogen containing reactant is reacted with the aminovinylsilane-based precursor.
 6. The method of claim 5 wherein thenitrogen containing reactant is selected from the group consisting ofammonia, nitrogen and mixtures thereof.
 7. The method of claim 1 whereinthe deposition is conducted at an elevated temperature at or below 500°C.
 8. The method of claim 1 wherein the deposition is conducted in thepresence of a diluent gas selected from the group consisting of helium,argon, neon, xenon and mixtures thereof.
 9. The method of claim 1wherein the flow rate of the amino vinylsilane-based precursor is 50 to1000 mg/min.
 10. The method of claim 5 wherein the flow rate of thenitrogen containing reactant is 500 to 10,000 mg/min.
 11. The method ofclaim 8 wherein the flow rate of the diluents gas is 50 to 50,000mg/min.
 12. The method of claim 1 wherein the deposited thin film has acompressive stress of −700 to −2400 MPa.
 13. The method of claim 1wherein the deposited thin film has a N—H to Si—H ratio of 25 to
 85. 14.The method of claim 1 wherein the deposited thin film has a N—H derivedH content/cm³×10²² in the range of 3.3 to 3.6.
 15. The method of claim 1wherein the deposited thin film has a compressive stress of −700 to−4500 MPa. 16-18. (canceled)
 19. A method for depositing a film selectedfrom a silicon nitride film or a silicon carbonitride film comprising:reacting a nitrogen-containing gas with a precursor having the generalformula:[RR¹N]_(x)SiR³ _(y)(R²)_(z) where x+y+z=4, x=1-3, y=0-2, and z=1-3 andwherein R, R¹ and R³ are individually selected from the group consistingof hydrogen, C₁ to C₁₀ alkane, O₂ to C₁₀ alkene, or C₄ to C₁₂ aromatic;R² is selected from the group consisting of a vinyl, allyl or othervinyl-containing functional group and wherein when R² is vinyl, x=2,y=0, and z=2, R and R¹ cannot both be methyl to provide the film. 20.The precursor of claim 19 selected from the group consisting ofBis(isopropylamino)divinylsilane (BIPADVS),Bis(isopropylamino)diallylsilane, Bis(t-butylamino)divinylsilane,Bis(t-butylamino)diallylsilane, Bis(diethylamino)diallylsilane,Bis(methyethylamino)diallylsilane, and Bis(methyethylamino)divinylsilane21. A composition for depositing a film selected from a silicon nitrideand a silicon carbonitride film comprising: an aminosilane precursorwhich is at least one selected from the group consisting ofBis(isopropylamino)divinylsilane (BIPADVS),Bis(isopropylamino)vinylmethylsilane (BIPAVNS),Bis(isopropylamino)vinylsilane, Bis(isopropylamino)allylmethylsilane,Bis(isopropylamino)allylsilane, Bis(t-butylamino)vinylmethylsilane,Bis(t-butylamino)vinylsilane, Bis(t-butylamino)allylmethylsilane,Bis(t-butylamino)allylsilane, Bis(diethylamino)vinylmethylsilane,Bis(diethylamino)divinylsilane, Bis(diethylamino)vinylsilane,Bis(diethylamino)allylmethylsilane, Bis(diethylamino)allylsilane,Bis(dimethylamino)vinylmethylsilane, Bis(dimethylamino)divinylsilane,Bis(dimethylamino)vinylsilane, Bis(dimethylamino)allylmethylsilane,Bis(dimethylamino)diallylsilane, Bis(dimethylamino)allylsilane,Bis(methylethylamino)vinylmethylsilane, Bis(methyethylamino)vinylsilane,Bis(methyethylamino)allylmethylsilane, Bis(methyethylamino)allylsilane,Dipiperidinovinylmethylsilane, Dipiperidinovinylsilane,Dipiperidinoallylmethylsilane, Dipiperidinodiallylsilane,Dipiperidinoallylsilane, Dipyrrolidinovinylmethylsilane,Dipyrrolidinovinylsilane, Dipyrrolidinoallylmethylsilane,Dipyrrolidinodiallylsilane, and Dipyrrolidinoallylsilane.
 22. Thecomposition of claim 21 further comprising a nitrogen-containing gas.23. The composition of claim 21 further comprising an inert gas.
 24. Amethod for depositing a film selected from a silicon nitride film or asilicon carbonitride film comprising: reacting a nitrogen-containing gaswith an aminosilane precursor to provide the film wherein the aminosilane precursor is at least one selected from the group consisting ofBis(isopropylamino)vinylmethylsilane (BIPAVNS),Bis(isopropylamino)vinylsilane, Bis(isopropylamino)allylmethylsilane,Bis(isopropylamino)allylsilane, Bis(t-butylamino)vinylmethylsilane,Bis(t-butylamino)vinylsilane, Bis(t-butylamino)allylmethylsilane,Bis(t-butylamino)allylsilane, Bis(diethylamino)vinylmethylsilane,Bis(diethylamino)divinylsilane, Bis(diethylamino)vinylsilane,Bis(diethylamino)allylmethylsilane, Bis(diethylamino)allylsilane,Bis(dimethylamino)vinylmethylsilane, Bis(dimethylamino)divinylsilane,Bis(dimethylamino)vinylsilane, Bis(dimethylamino)allylmethylsilane,Bis(dimethylamino)diallylsilane, Bis(dimethylamino)allylsilane,Bis(methylethylamino)vinylmethylsilane, Bis(methyethylamino)vinylsilane,Bis(methyethylamino)allylmethylsilane, Bis(methyethylamino)allylsilane,Dipiperidinovinylmethylsilane, Dipiperidinovinylsilane,Dipiperidinoallylmethylsilane, Dipiperidinodiallylsilane,Dipiperidinoallylsilane, Dipyrrolidinovinylmethylsilane,Dipyrrolidinovinylsilane, Dipyrrolidinoallylmethylsilane,Dipyrrolidinodiallylsilane, and Dipyrrolidinoallylsilane.